Usually lubrication of a bearing is done with a lubricant like oil which is pumped by an electrical or mechanical pump through the bearing. Normally the oil is collected at the lowest part of the bearing and pumped to the highest part. From the highest part the oil gets distributed by the movement of the bearing and flows down to the lowest part due to gravity.
For a bearing with a rotating outer ring and a stationary inner ring the bearing is not very good accessible in the lowest part because of the outer rotating parts.